1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method and a computer readable memory medium storing an image processing program, for embedding watermark information in image data.
2. Related Background Art
For image recording/reproduction, there has conventionally been known the video cassette recorder which records an analog image signal on a magnetic tape, but copyright issues relating to illegal or improper use of image data has not been raised seriously with such apparatus because the image is deteriorated by repeated copying.
On the other hand, digital image data, formed by digitizing an image signal with eventual compression encoding, is easily handled and not only can be recorded on a magnetic tape in a digital VCR but also can be stored in a computer memory or transmitted through a communication channel. Illegal use is a serious concern for such digitized image data because such data is mostly free from image deterioration even after recording or transmission.
For avoiding such illegal use, it is already known to incorporate, in the image, a digital watermark constituting ID information data for the author, distribution source, management number, distribution channel etc. of the image data. The digital watermarking is to secretly conceal the watermark data into the image, undiscernibly to the user observing the image, in order to later confirm the source or channel of distribution of the illegally used image. In such watermarking, it is important to minimize the image deterioration resulting from the concealing of the watermark data, to conceal the watermark data in such a manner that such watermark alone cannot be extracted from the image, and to avoid a significant increase in the amount of information by the concealing of the watermark data.
In digital watermarking for a moving image, it is proposed to conceal the watermark data only in a part of the frames, since the amount of the watermark data becomes very large if such data is concealed in every frame. However, if the interval of the watermarked frames is made excessively large, the effectiveness of prevention from illegal use becomes lower in the case where only part of the moving image is used.
In the above-mentioned method of concealing the digital watermark in a part of the frames of the moving image, if the digital watermark is concealed over several frames in an area that does not deteriorate the image, there will result a drawback that not only the concealing of such digital watermark but also the position thereof become obvious through comparison of the image data of those frames with image data of the preceding or succeeding frames, because the change in the image data though the image itself is not deteriorated. Consequently it also becomes easy to extract only the watermark, for example by eliminating the watermarked frame.
In consideration of the foregoing, an object of the present invention is to provide an image processing apparatus, an image processing method and a computer readable memory medium storing a program for such image processing, capable of concealing watermark information in image data with an increased resistance to attack while suppressing image deterioration and increase in the data amount.
To attain the above-mentioned object according to one aspect of the present invention, there is provided an image processing apparatus/method in which image data is input, the motion of such image data is discriminated and watermark information is superposed with predetermined information data according to the result of the discrimination.
According to an another aspect of the present invention, there is provided a computer readable memory medium storing a program for executing an input step of entering image data, a discrimination step of discriminating motion of the image data, and a superposing step of superposing watermark information with predetermined information data according to the result of the discrimination.
Other objects of the invention, and features and advantages thereof, will become fully apparent from the following detailed description to be taken in conjunction with the accompanying drawings.